EyeWorld Asia-Pacific September 2012 Issue

September 2012 19 EWAP FEAturE Topography of crosslinking and PRK Source: A. John Kanellopoulos, MD Tricks for avoiDing inTraoperaTive ingrowTh Indications for this combined procedure would be patients who are contact lens intolerant with poor spectacle-corrected vision, with the intention to improve the corneal topography for better contact lens tolerance or spectacle tolerance, Dr. Hersh said. The contraindications would be patients whose corneas are too thin (less than 400 microns) for either the crosslinking or Intacs procedure and patients who have corneal scarring, which would preclude an advantageous visual response to the procedures, he said. Crosslinking and LASIK In order to ameliorate the risk of ectasia after LASIK, some surgeons in Europe have also begun employing corneal crosslinking following the refractive surgery, with reportedly good results so far, Dr. Hersh said. Patients who may have a greater risk of corneal ectasia include those with thinner corneas or higher corrections, and there are investigators who have incorporated this for hyperopic procedures, which may tend to be less stable over time as well, he said. Dr. Kanellopoulos, who performs this combination surgery, said, “We currently use as an indication any patient who’s under 35 years old with myopia over 6.0 D and any patient with astigmatism over 1.0 D.” In a paper presented at the 2012 ASCRS•ASOA Symposium & Congress in Chicago, Dr. LIM Li, MD Senior Consultant and Head, Corneal and External Eye Disease Service Singapore National Eye Centre 11 Third Hospital Avenue, Singapore 168751 Tel. no. +65-62277255 lim.li@snec.com.sg M ost studies report that corneal collagen crosslinking is effective in stabilizing corneal ectatic conditions such as keratoconus and post-LASIK keratectasia. However, the majority of patients experience only slight improvement in vision and most still need to wear specialty rigid lenses for good vision. Visual rehabilitation following crosslinking remains a challenge. Various non- keratoplasty surgical techniques have emerged involving a combination of crosslinking for stabilization of the ectasia and another procedure for vision correction. These reports are usually case series studies and larger long-term studies are required. Kanellopouolos 1 and Kymionis 2 report encouraging results with simultaneous topography-guided photorefractive keratectomy (PRK) followed by corneal collagen crosslinking. The treatment involved customized laser ablation with conservative corneal tissue removal. The concern about surface ablation for keratoconus treatment is aggravation of the ectasia by further thinning of the cornea. The visual outcome for combined crosslinking and corneal intrastromal ring insertion is variable and a recent case series by Henriquez 3 showed good visual outcome at 6 months. Recently, a new indication for crosslinking has emerged: prophylaxis for LASIK ectasia in LASIK candidates. Accelerated crosslinking is now being used as an adjunctive treatment after LASIK. Celik 4 reported in a case series of 8 eyes (fellow eye as control) that the LASIK–CXL group had equal or better visual outcome than the LASIK only group. Kanellopuolos 5 also reported long-term safety and efficacy in prophylactic accelerated crosslinking in LASIK candidates. In summary, while crosslinking makes the ectatic cornea more biomechanically stable, surgical visual rehabilitation remains a challenge and rigid lens wear is still the best option with the best visual outcome for contact lens-tolerant patients. Combined procedures (crosslinking and PRK/intrastromal rings) have reasonable visual outcome in selected patients and further validation studies are required. In advanced keratoconus with significant corneal thinning and scarring, deep lamellar keratoplasty should be considered. Prophylactic crosslinking in LASIK is a new emerging technique which requires long-term follow-up and evaluation. References 1. Kanellopoulos AJ, Binder PS. Management of corneal ectasia after LASIK with combined, same-day, topography-guided partial transepithelial PRK and collagen cross-linking: the Athens protocol. J Refract Surg. 2011 May;27(5):323-31. 2. Kymionis GD, Portaliou DM, Kounis GA, et al. Simultaneous topography-guided photorefractive keratectomy followed by corneal collagen cross-linking for keratoconus. Am J Ophthalmol. 2011 Nov;152(5):748-55. Epub 2011 Jul 26. 3. Henriquez MA, Izquierdo L Jr., Bernilla C, et al. Corneal collagen cross-linking before ferrara intrastromal corneal ring implantation for the treatment of progressive keratoconus. Cornea 2012 Jul;31(7):740-5. 4. Celik HU, Alagöz N, Yildirim Y, et al. Accelerated corneal crosslinking concurrent with laser in situ keratomileusis. J Cataract Refract Surg. 2012 Aug;38(8):1424-31. 5. Kanellopoulos AJ. Long-term safety and efficacy follow-up of prophylactic higher fluence collagen cross-linking in high myopic laser-assisted in situ keratomileusis. Clin Ophthalmol. 2012;6:1125-1130. Epub 2012 Jul 18. Editors’ note: Dr. Lim has no financial interests related to her comments. Views from Asia-Pacific Kanellopoulos and colleagues reported the results of a contralateral eye study where one eye had standard hyperopic LASIK and the other had hyperopic LASIK with prophylactic collagen crosslinking. The study showed statistically significant evidence that the latter group preserved steeper corneal effect consistent with the stability of the initial hyperopic correction, Dr. Kanellopoulos said. Besides the extra time and expense involved in this procedure, Dr. Kanellopoulos said there aren’t really any drawbacks. However, contraindications include ultrathin flap LASIK. Flaps that are under 100 μ may get some wrinkling because some of the riboflavin solution soaks into the flap and may result in microstriae, he said. With most LASIK studies reporting that the biomechanical stability of the cornea inherently weakens by 20% in the long term, Dr. Kanellopoulos said that the prophylactic application of corneal crosslinking will only benefit the long-term behavior and stability of the cornea in LASIK procedures. EWAP Editors’ note: Drs. Hersh and Kanellopoulos have no financial interests related to this article. Contact information Hersh: +1-201-883-0505, phersh@vision-institute.com Kanellopoulos: +30-21-07-47-27-77, ajk@laservision.gr